This is a problem that I am trying to solve for years, periodically spending 1-2 months on it.
I am using Metrowerks IDE and ColdFire C compiler MCFCCompiler ver 4.0 to build the embedded code that uses the USB module for communication with the host. The product with this hardware has been out for eight years and pretty successful. However, along these years we were getting complaints from the field that occasionally the communication with the host hangs up and the operation is unrecoverable.
I tracked the bug down using USB sniffer and the Coldfire debug hardware and this is condition and the scenario that I find the code in.
The communication break is on the firmware side and not the driver on the host.
The hang-up happens only when sending USB firmware commands from host (windows 7) in rapid-fire from multiple threads. Every firmware command replies back to the host. So there's maximum traffic through the USB port.
I am using the implementation provided by Motorola that is well documented in USB-STAND-ALONE-DRIVER_V03.pdf (google will find it for you). There are two functions that are in my focus point and they should play nicely together: usb_in_service (called by the interrupt handler) and usb_tx_data (that initiates the transfer, which at some point will generate an interrupt).
The usb_tx_data function is implemented such that it bails out if the USB fifo still has data to send to the host. But waiting on the fifo to clear up takes the code into an infinite loop.
No more interrupt occurs after this although the USB module's registers content tells me the interrupts are enabled.
I checked that the USB module did not get reset event and is not suspended either.
The main question is whether the error is in the USB module hardware or in the code. I don't find any errata pointing to this problem. If it's the code, where is that whole in it that the logic is not accounting for?
The hot pursuit in on because we are making a new line of product based on this same firmware and I cannot release it until this is solved.
